Background – Cortisol is a key hormone in the response to stress, and depression, anxiety and stress are associated with increased daily cortisol secretion. Dietary factors may influence daily cortisol secretion.
Objective – To assess the effect on cortisol secretion of two diets: a high-calcium diet, rich in low-fat dairy foods (HC) and a low-sodium, high-potassium diet, rich in fruits and vegetables (LNAHK) with a moderate-sodium, high- potassium, high-calcium “DASH” type diet, high in fruits, vegetables and low-fat dairy foods (OD).
Design - In a crossover design, subjects were randomised to two test diets for 4- wk, the OD and either HC or
LNAHK, each preceded by a 2 wk control diet (CD). Saliva samples were collected in the morning and at 1200 h,
1600 h, 2000 h for 1 d at the end of each diet.
Outcomes – Seventy-four subjects completed the study (29 men, 45 women) with a mean (SD) age of 56.3(9.8) yr 2
and a mean BMI of 29.2(3.8) kg/m . Cortisol variability was high for morning samples (176% CV); however, afternoon/evening samples (area under the curve (AUC) (nmol.l-1 .8hr-1 )) had less variation (30% CV). CD cortisol concentrations predicted the change in AUC: for the OD ß=-0.8(0.1) (SEM), LNAHK ß=-0.7(0.1) and HC ß=-0.7(0.1) (R2 : 0.4-0.6). The % change in AUC was lower in the HC diet when compared to the OD diet (P=0.058),
and significantly lower when compared to the LNAHK diet (P<0.05).Conclusion – Consumption of 3-4 serves/day of dairy foods resulted in a fall in cortisol secretion compared to a rise seen in two diets requiring some dietary restrictions. This suggests increased dairy intake may have beneficial effects on cortisol secretion in the afternoon/evening period.